Cross-dressing Week: Madam Fatal
As suggested here, let's declare it official Cross-dressing Week! And where better place to start than with Golden Age "heroine" Madam Fatal?

Introduced in the appropriately named Crack Comics #1 in 1940, elderly matron Madam Fatal (think Aunt May, but with... added extras) is really retired actor Richard Stanton. When his daughter is kidnapped, he sets about making a new life for himself as an old woman. His foes now underestimate his speed and strength allowing him to fight crime™. No one knows of his secret but his pet bird, a parrot named Hamlet.

I'm providing the entirety of Madam Fatal's origin story as, according to the website I downloaded this from (www.goldenagecomics.co.uk) Crack Comics #1 has been verified as being public domain.

Although, I suspect the continuing cross-dressing had more to do with the enjoyment of being able to do stuff like this:

Rarely has a sound effect been more appropriate either.

So Madam Fatal went on to star in another 22 issues of Crack Comics, building up an army of villainous rivals including DOCTOR PROWL!

And THE JESTER! (Here's that sound effect again.)

Building slash opportunities along the way.

Apparently, Madam Fatal has only ever been mentioned once as part of the DCU, in 1999's JSA #1 at the funeral of Wes Dodds by Wildcat.

Poor Madam Fatal. Dress up as a woman a few times to fight crime and they just make you into a gay joke.